Jesse Custer (Dominic Cooper), Tulip O'Hare (Ruth Negga) and Cassidy the Vampire (Joseph Gilgun) are hitting the highway on a quest for God. But while the trio seem to be thick as thieves, that unity sounds like it's going to be short-lived.

ET recently caught up with the stars of the acclaimed series, where they shared a glimpse of what fans can look forward to (or possibly dread) from their grim journey.

"It's a great sort of cozy idea that the three of them are happy at last, having found friendship and comfort and a life that they've really missed, and there's an excitement between them. They've found sort of a purpose," Cooper explained. "But you know that they're lying to each other."

Jesse is a criminal-turned-Preacher who returned to minister his dead father's church in the small, bleak town of Annville, Texas. He's also the host to a mysterious entity called Genesis, which gives him a power he calls the "Word of God," and he can use it to make anyone do anything he says.

Tulip is a rough-and-tumble criminal with a dark past who used to be in a relationship with Jesse until something happened in their past that tore them apart. After coming back to Annville, Tulip spends most of the first season reacquainting with Jesse and being the devil on his shoulder.

Meanwhile, Cassidy is a 119-year-old vampire who literally lands in Annville after jumping out of a plane without a parachute. After befriending Jesse, Cassidy becomes one of his most dedicated allies.

In the season finale, Jesse discovers that God has abandoned heaven and the three of them hit the road on a journey to find God and make him account for his actions. However, the news that God has abandoned his creations doesn't sit well with the citizens of Annville, and the news drives them all insane.

Hours after Jesse, Tulip and Cassidy leave, a freak accident causes the entire town to blow up, killing off basically every secondary character on the show in an apocalyptic explosion. So, this new season is kind of a clean slate.

However, Cooper explained that, despite how cozy Jesse and his pals seem now, they're on a mission: "There's stuff that they're not telling one another."

"It's under the guise of a fun road trip with mates, but you know full well, that in the confined space of this car… that those very powerful, distinctive personalities are going to be at loggerheads with one another," he teased. "And that's what we feel is kind of bubbling under the surface in the beginning."

One thing that has defined Preacher is its wildly varying tones. In some scenes, the series is a bleak and existential examination of human nature and the meaning of faith, and other times it's slapstick, gore-filled horror comedy. For Cooper, that unpredictability continues just as boldly in the coming season.

"One minute, you're having a very serious debate or a reflective moment about your history," he said, "and then, within seconds, you're fighting or dealing with a conversation about foreskins or [battling] an unknown entity that's beyond the realms of possibility in our world as we know it."

One of the major sources of tension this season is the unspoken love triangle between Jesse and Tulip -- who have rekindled their relationship -- and Cassidy, who slept with Tulip midway through season one, before he knew she was his new friend's ex.

According to Gilgun, Cassidy "feels dreadful" about his fling with Tulip, and he wants to fess up to Jesse to clear his conscience, but he's also battling the residual feelings he still harbors for her.

"He wants to say, 'Listen, I didn’t know and I'm sorry. And I'm sorry I even feel anything for her now. I've tried to not feel that way, and I just can't,'" Gilgun explained. "It's not like there's any agenda or any malicious intent behind it. He's not trying to split anyone up."

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Cassidy has perhaps had the biggest arc of anyone on the show -- going from a blood-thirsty drugged-out lunatic to a kinder, more conscientious friend who legitimately wants to help Jesse on his mission.

"This year has been very different. [We've seen] a different version of Cassidy. He's kind of a bit more domesticated this year. He's got responsibilities this year, and it's been a challenge," Gilgun shared.

As much as Gilgun loved "the fighting, the drinking, and the drugs" in past episodes, he admitted he's felt much more fulfilled portraying a more complex Cassidy in the second season.

"As an actor, you have to play a light and dark and sometimes you have to go to some dark places," Gilgun said. "Cassidy has been desperately trying to repent, since meeting Jesse. He's having a go at it. It doesn't work out, surprisingly, but at least he has a go."

Since his character has calmed down a bit, it means Gilgun hasn't had as many scenes in which he's drenched head to toe in fake blood and gore, and he actually misses it.

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"I had accepted it as part of my role and I was proud of it. I was proud of my [bloody] handprints around the set. Proud of the fact that you could find me from a trail [of fake gore]. I loved being the Vampire," he said. "This season, there's not been as much blood, I have to say. There's been moments, there's been windows of it, but I'd like to see a lot more."

As for Negga, the tension between Tulip and Jesse is building as well, and it's all due to Jesse's mind-controlling superpower and his single-minded determination to find and judge God himself.

"It's an aberration for him to go on this quest, because it's not him and it's not how she envisions anyone she loves being," Negga explained. "It just doesn't make any sense to her."
In her mind, Jesse's immense power is a "corrupting influence," and Tulip's trying -- and often failing -- to be his moral compass.

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"Even if one thinks [what they're doing is] for the greater good, how does one know if there's no one to check it? And [Tulip] is trying to check it but how do you battle someone who is on a mission and has a singular vision of what they're supposed to do and really believes it? That’s where the tension in their relationship comes from, and the distancing," she said.

Although it doesn't help that Tulip has a few dark secrets in her past that come to light as the trio look for the Lord Almighty in the beautiful city of New Orleans.

While on their journey, Jesse, Tulip and Cassidy only have each other to rely on -- but with a whole lot of villians coming out of the woodwork this season, things are going to get even more dangerous than ever before. However, Cooper says he's looking forward to getting to kick some more ass.

"[The fights] really underline who [Jesse] is," he said. "He's a man who's just an addict, and when you see him finally give in to a fight, you see that kind of joy and that release. And I've loved doing them, and there's more and more in this next [season]."